Chcetophoracece 85 



pairs. The resultant zygospores usually undergo a short period 

 of rest before germination. 



Genus Chaetophora Schrank, 1789. The thallus is gelatinous, 

 macroscopic, of a tough consistency, and of some definite form. 

 The filaments radiate out from a central point, those nearest the 

 centre being little branched, but carrying at their apices dense 

 clusters of corymbiform branches of a very bright green colour. 

 The terminal cells of the branches are often prolonged into long 

 hyaline hairs. The zoogonidia possess two or four cilia, and the 

 hypnospores are brown, being generally developed from the terminal 

 cells of the branches. Many of these plants, particularly certain 

 species 1 , have the power of extracting calcium carbonate from the 

 water in which they live and so giving rise to incrustations of 

 considerable thickness. 



The most abundant species of the genus is Ch. pisiformis (Roth) Ag., an 

 Alga which occurs as hemispherical, or almost spherical, dark green masses 

 attached to submerged stones or to the submerged parts of plants. It is also 

 often found attached to the shells of aquatic Gastropods. Its distinguishing 

 features are the absence of terminal hairs and the slightly torulose character 

 of cells of the branches; the cells of the primary filaments are 9 15 p, in 

 diameter. The next most abundant species is Ch. incrassata (Hudson) Hazen 

 [ = Ch. endivcefolia Ag. ; Ch. Cornu Damce (Both) Ag.], which possesses a tough, 

 gelatinous, sub-dichotomously branched thallus, rather flat and of a darker green 

 at the periphery than in the centre (fig. 27 A and B). The branched thallus 

 bears much resemblance to the horns of a stag and in adult specimens is 

 frequently found floating freely at the marshy margins of poods and lakes, or 

 even in bogs. Ch. tuberculosa (Roth) Ag. possesses a large cushion-shaped 

 thallus from 2 to 4 (or even 5) cms. in diameter, occurring usually in marshes 

 or in bogs. Ch. elegans (Roth) Ag. is a rarer species than the three previous 

 ones and occurs as very pale-green masses, clinging to submerged stems and 

 leaves of grasses, sedges, or mosses (fig. 27 C). 



Genus Myxonema Fries, 1825. [Stigeoclonium Ktitz., 1843.] 

 The thallus is filamentous, branched, and usually devoid of the 

 great mass of gelatinous material which is so conspicuous a feature 

 of Chcetophora. The branches are scattered, more or less isolated, 

 and often very elongated, but they are rarely developed in dense 

 fasciculate groups. The main branches bear other, shorter, lateral 

 branches which are either acuminate or terminate in long hyaline 

 hairs. There is usually a creeping portion of the thallus, attached 

 to some substratum, but adult plants frequently float freely in 



1 Forms of Ch. incrassata and Ch. elegans are often met with encrusted with 

 lime. A form of the latter species was recently named by Tilden Ch. calcarea. 

 Vide Tilden in Botan. Gazette, 1897, pp. 97100, 102, 



